U.S. patent number 4,628,454 [Application Number 06/496,566] was granted by the patent office on 1986-12-09 for automatic running work vehicle.
This patent grant is currently assigned to Kubota, Ltd.. Invention is credited to Katsumi Ito.
United States Patent |
4,628,454 |
Ito |
December 9, 1986 |
Automatic running work vehicle
Abstract
An automatic running work vehicle which is adapted to repeat a
running travel reciprocatingly and which has means for teaching the
running course of one travel by sampling the running direction
detected by an orientation sensor every predetermined running
distance detected by a distance sensor during the travel and for
steering the work vehicle based on the information of running
course taught by the preceding travel when follower sensors fail to
detect the boundary of the running course for a predetermined
period of time.
Inventors: |
Ito; Katsumi (Osaka,
JP) |
Assignee: |
Kubota, Ltd. (Osaka,
JP)
|
Family
ID: |
14814374 |
Appl.
No.: |
06/496,566 |
Filed: |
May 20, 1983 |
Foreign Application Priority Data
|
|
|
|
|
Jul 13, 1982 [JP] |
|
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57-121565 |
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Current U.S.
Class: |
701/25;
180/168 |
Current CPC
Class: |
A01B
69/008 (20130101); G05D 1/0259 (20130101); G05D
2201/0208 (20130101); G05D 1/0272 (20130101) |
Current International
Class: |
A01B
69/04 (20060101); G05D 1/02 (20060101); G06F
015/50 (); B62D 001/28 () |
Field of
Search: |
;364/424,449,450,460
;318/578 ;180/167,168,169 ;901/1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Stauffer: Heath's New Training Robot Interacts with Environment,
Robotics Today, Dec. 1982, pp. 37,38..
|
Primary Examiner: Gruber; Felix D.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Claims
I claim:
1. An automatic running work vehicle controllable to travel along a
series of parallel straight courses on a defined work site,
following a boundary between a worked area and an unworked area,
and to reverse its travelling direction at an end of each of the
courses, said vehicle comprising:
a plurality of position sensor means for detecting said boundary
and a beginning and an end of said courses,
transmitter means for transmitting a pulse per unit of travelling
distance upon detection of said beginning of the course by said
position sensor means, and for continuing to transmit said pulse
per unit of travelling distance until detection of said end of the
course by said position sensor means,
orientation sensor means for detecting the travelling direction of
the vehicle and for transmitting an orientation signal,
storing means for (i) counting the pulses when the vehicle starts
running along the straight course, (ii) receiving said orientation
signal when the count reaches a predetermined value, (iii)
successively sotring in order, pairs of data, each pair consisting
of running distance data corresponding to said count and
orientation data, and (iv) successively reading out said pairs of
the data in reverse order to said order of storing said data, when
the travelling direction of the vehicle is reversed at the end of
said course, and
steering control means operatively connected to said position
sensor means and said storing means for (a) steering said vehicle
along said boundary in accordance with the detection of said
boundary by said position sensor means and (b) steering said
vehicle in accordance with said stored pairs of data in response to
said boundary remaining undetected by said position sensor means
for a predetermined time.
2. An automatic running work vehicle as in claim 1 wherein said
storing means includes memory means and addressing means for
storing said pairs of data in an address assigned by said
addressing means, said addressing means incrementing said address
when the vehicle travels in a forward direction and decrementing
said address when the vehicle travels in a reverse direction.
3. An automatic running work vehicle as in claim 1 wherein said
storing means includes memory means and addressing means, and
wherein said pairs of data stored while each course is traveled are
blocks transferred into a reversed order when the vehicle is
reversed at the end of said each course.
4. An automatic running work vehicle as in claim 1 wherein said
orientation sensor means detects a steering direction and an
angular deflection of front wheels corresponding to an amount of
steering of the vehicle.
5. An automatic running work vehicle controllable to travel along a
series of parallel straight courses on a defined work site,
following a boundary between a worked area and an unworked area,
and to reverse its travelling direction at an end of each of the
courses, said vehicle comprising:
a plurality of position sensor means for detecting said boundary
and a beginning and an end of said courses,
transmitter means for transmitting a pulse per unit of travelling
distance upon detection of said beginning of the course by said
position sensor means, and for continuing to transmit said pulse
per unit of travelling distance until detection of said end of the
course by said position sensor means,
orientation sensor means for detecting the travelling direction of
the vehicle and for transmitting orientation data, and
a control unit including a memory, an input interface connected to
said position sensor means, said transmitter means and said
orientation sensor means, and an output interface connected to
steering means,
said control unit being adapted to transmit to said steering means
a signal in accordance with signals from said position sensor means
for steering said vehicle along said boundary, to count said pulses
received from said transmitter means, and to store in said memory
said orientation data received from said orientation sensor as
associated with said count while said vehicle runs from said
beginning to said end of said course, and when said boundary
remains undetected by said position sensor means for a
predetermined time, said control unit transmits to said steering
means a signal in accordance with orientation data associated with
a count reached during a preceding straight course running and
corresponding to a count reached upon lapse of said predetermined
time.
6. An automatic running work vehicle as in claim 5 wherein said
storing means includes memory means and addressing means, and
wherein said travelling distance data and said orientation data
stored while each course is travelled are blocks of information,
transferred into a reversed order when the vehicle is reversed at
the end of said course.
7. An automatic running work vehicle as in claim 5 wherein said
orientation sensor means detects a steering direction and an
angular deflection of front wheels corresponding to an amount of
steering of the vehicle.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automatic running work vehicle,
and more particularly to such a work vehicle which is adapted to
perform work on the ground of a work site while repeating a running
travel reciprocatingly and which has follower sensors for detecting
the boundary between a worked area and an unworked area for each
travel so as to run along the boundary automatically.
2. Description of the Prior Art
With automatic running work vehicles of this type heretofore known,
sensors are mounted on the vehicle body for detecting the
boundaries of running areas to automatically steer the wheels along
the boundary detected by the sensors and automatically run the
vehicle on a predetermined course along the boundary under follower
control.
According to the conventional mode of follower control, however,
the vehicle is merely so controlled as to automatically cover a
specified work site by performing each of reciprocating travels
along the boundary between the unworked area and the area already
worked on by the preceding travel, so that there is the following
drawback.
When the boundary defining a running course has a break, for
example, due to the presence of an obstacle or absence of the
object to be worked on, it is impossible to run the vehicle under
continued follower control, with the result that the vehicle
deviates greatly from the specified running course.
SUMMARY OF THE INVENTION
An object of the present invention, which has been accomplished in
view of the above problem, is to provide a work vehicle which is
adapted to run automatically with good stability at all times
without greatly deviating from the contemplated running course even
if the course has at an intermediate portion thereof an obstacle or
an area where the object to be worked on is absent.
To fulfill this object, the automatic running work vehicle of the
invention is adapted to repeat a running travel reciprocatingly and
has follower sensors for detecting the boundary between a worked
area and an unworked area for each travel. The work vehicle is
characterized in that it is provided with a distance sensor for
detecting the running distance of its body, an orientation sensor
for detecting the running direction thereof, and means for teaching
the running course of one travel by sampling the running direction
detected by the orientation sensor every predetermined running
distance detected by the distance sensor during the travel and for
steering the work vehicle based on the information of running
course obtained by the teaching of the preceding travel when the
follower sensors fail to detect the boundary for a predetermined
period of time.
Because of the above feature, the work vehicle has the following
great advantage.
When the follower sensors become no longer able to detect the
boundary of the running area during running, the vehicle runs
automatically based on the information of teaching obtained in the
preceding travel, so that the vehicle can be driven automatically
with good stability without deviating greatly from the specified
running course.
Other objects and advantages of the present invention will become
apparent from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an overall side elevation showing a mower as an unmanned
work vehicle embodying the invention;
FIG. 2 is an overall plan view showing the mower;
FIG. 3 is a fragmentary front view showing a follower sensor;
FIG. 4 is a diagram showing a specified running course;
FIG. 5 is a block diagram showing a control system;
FIGS. 6 (A) and (B) are diagrams each showing how to detour an
obstacle; and
FIGS. 7 (A) to (D) are a flow chart showing the operation of the
control system.
DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to FIGS. 1 and 2, a vehicle body 1 has a mower
assembly 4 vertically movably suspended therefrom and positioned
between its front and rear wheels 2, 3. The vehicle body 1 further
has on opposite sides of its front portion follower sensors 5A, 5B
having the construction to be described below for detecting the
boundary of a running area, i.e., the boundary between an unmowed
area and a mowed area. Thus the mower is steered along the boundary
detected by the follower sensors 5A, 5B to automatically run a
specified running course.
The mower is further provided ahead of its body 1 with an obstacle
sensor 6 of the non-contact type for detecting obstacles on the
running course.
Additionally the vehicle body 1 has a fifth wheel 7A serving as a
distance sensor 7 for generating a pulse per optional unit running
distance K to continuously detect the distance of travel of the
vehicle body 1, and an orientation sensor 8 for detecting the
running direction of the body 1.
Usually the front wheels 2, 2 are adapted to be steered rightward
or leftward by a hydraulic cylinder 9 by a predetermined amount
based on the result of detection of the boundary by the follower
sensors 5A, 5B or on the result of detection of an obstacle by the
sensor 6.
Each of the follower sensors 5A, 5B comprises a pair of
photosensors S.sub.1, S.sub.2 (S'.sub.1, S'.sub.2) of identical
structure disposed ahead of each side of the mower assembly 4.
FIG. 3 shows the structure of the photosensors S.sub.1, S.sub.2
(S'.sub.1, S'.sub.2). A sensor mount frame 11 attached to the mower
assembly 4 is fixedly provided with substantially U-shaped sensor
frames 10, 10 arranged side by side laterally of the vehicle body
1. Each sensor frame 10 has a pair of light-emitting element
P.sub.1 and photocell P.sub.2 on the opposed inner sides thereof
for detecting the presence or absence of grass to be brought into
the space therebetween with the travel of the vehicle body 1 to
detect the boundary between the mowed area and the unmowed
area.
It is seen in FIG. 4 that when the follower sensor 5A composed of
the photosensors S.sub.1, S.sub.2 or the follower sensor 5B
composed of the photosensor S'.sub.1, S'.sub.2 is in the unmowed
area 12B, the vehicle is so steered for running that the outer
photosensor S.sub.2 or S'.sub.2 only of the other follower sensor
is positioned in the mowed area 12C. Upon reaching a turning area
12D around the mowing area 12A, the vehicle is turned toward the
follower sensor which has been in the unmowed area 12B. The turning
area 12D is made a mowed area in advance by non-automatically
driving the mower. Upon the arrival of the vehicle at the turning
area 12D, all the four photosensors S.sub.1, S.sub.2 and S'.sub.1,
S'.sub.2 constituting the follower sensors 5A, 5B detect the mowed
area, indicating the arrival.
The follower sensors 5A, 5B are not limited to those comprising
photosensors S.sub.1, S.sub.2 and S'.sub.1, S'.sub.2 but can be
composed of other sensors of the non-contact, contact or any other
type.
The obstacle sensor 6 comprises four contact members 6a, 6b, 6c, 6d
arranged ahead of the vehicle body 1 approximately over the entire
width of the body 1 therealong, usually biased forward and each
individually turnable rearward by contact with an obstacle, and
switches S.sub.3, . . . provided at the base ends 6e, . . . thereof
for detecting the turn of the contact members 6a, 6b, 6c, 6d,
respectively.
The position where an obstacle comes into contact with the sensor 6
is detectable in four divided ranges corresponding to the operative
positions of the switches S.sub.3, . . .
The orientation sensor 8 comprises a potentiometer 8a mounted on an
axle portion of the front wheels 2, 2 for detecting the steering
direction and the amount of steering, i.e., the angular deflection
of the front wheels. The orientation sensor 8, which is thus
adapted to detect the steering angle of the front wheels 2, 2, may
alternatively be adapted to detect the running direction of the
fifth wheel 7A serving as the distance sensor 7. Also usable is a
sensor of some other type, such as one which detects the running
direction of the vehicle body 1 by sensing the geomagnetism. In
brief, the sensor may be of any type insofar as it is capable of
detecting the running direction of the vehicle body 1.
The control system will be described below for automatically
controlling the running of the mower based on the detection signals
from the sensors 5A, 5B, 6, 7 and 8 of the foregoing
constructions.
With reference to FIG. 5, the control system comprises an
arithmetic control unit 13 the main portion of which is a
microcomputer. The signals from the follower sensors 5A, 5B, the
obstacle sensor 6, the distance sensor 7 and the orientation sensor
8 are fed to the unit 13 via an input interface 14. Based on the
signals from these sensors, the unit 13 performs an arithmetic
operation and gives the result, i.e., control signals, to an output
interface 17 to cause an electromagnetic valve 15 to drive the
hydraulic cylinder 9 which is an actuator, thus operating the front
wheels 2, 2 and a speed change unit 16.
Usually the control system steers the front wheels 2, 2 in response
to the signals from the follower sensors 5A, 5B which discrimanate
between the unmowed area 12B and the mowed area 12C to run the
vehicle body along the boundary therebetween in the mowing area 12A
under follower control as seen in FIG. 4.
When the obstacle sensor 6 detects an obstacle 12E on the running
course surrounded by the turning area 12D during running, the
vehicle body is subjected to obstacle detouring control as shown in
FIG. 6 (A) or (B) in preference to the follower control based on
the detection signals from the follower sensors 5A, 5B.
The obstacle detouring control will be described below.
When one of the switches S.sub.3, . . . of the obstacle sensor 6 is
turned on upon detecting an obstacle, the follower control is
interrupted, and the speed change unit 16 is operated to
temporarily stop the vehicle body 1. The switch S.sub.3 actuated is
identified to determine which of the contact members 6a, 6b, 6c, 6d
has come into contact with the obstacle. If the contact member 6b
or 6c in the center is in contact therewith, the vehicle body 1 is
retracted a predetermined distance once and then advanced as
steered toward a given direction as shown in FIG. 6 (A). When the
vehicle body is to be thus retracted temporarily, the data
indicating the particular contact member in contact with the
obstacle is temporarily stored in the memory 25, via the addressing
unit 30 to determine the detouring direction, and the vehicle is
thereafter steered in the detouring direction immediately before it
is advanced. The detouring direction determined is toward one side
opposite the particular contact member concerned.
If only one of the outer members 6a, 6d has come into contact with
the obstacle, the vehicle is advanced as steered toward a direction
opposite to that member as shown in FIG. 6 (B).
After the vehicle has been brought into the advance travel for
detouring the obstacle, the vehicle is steered according to the
running course information obtained by teaching in the course of
the preceding travel as will be described later, to automatically
return to the running course before the detouring. The control by
the follower sensors 5A, 5B is thereafter resumed to automatically
drive the vehicle in the specified direction.
The information as to the course run by the vehicle under the
follower control as well as under the obstacle detouring control
will be sampled processed by the addressing unit 30 and stored in
the memory 25 for teaching in the following manner.
As shown in FIG. 7 (D), the running course sampling is an interrupt
process which is initiated most preferentially in response to a
pulse count signal emitted by the distance sensor 7 every
predetermined distance of travel, l.sub.0, which is predetermined
as the sampling interval for the running course.
With reference to FIG. 7 (A), the overall control program is so
designed as to sample and store the running course information for
every travel which is initiated upon the detection of the unmowed
area 12B by one of the photosensors S.sub.1, S.sub.2, S'.sub.1,
S'.sub.2 constituting the follower sensors 5A, 5B with the advance
of the vehicle body 1 from the turning area 12D into the unmowed
area 12B shown in FIG. 4 and which is completed when the mowed
turning area 12D is detected by all the photosensors S.sub.1,
S.sub.2, S'.sub.1, S'.sub.2.
More specifically stated, when the vehicle body 1 starts running
under follower control from one end of the turning area 12D around
the unmowed area 12B, a counter simultaneously starts counting up
the pulse signals from the distance sensor 7, and every time the
vehicle body 1 has run the predetermined distance l.sub.0, the
running direction .theta. detected by the orientation sensor 8 at
that time and the total distance l of travel after the start of
counting are incrementally addressed by the addressing unit 30, and
stored in a specified memory area within the control unit 13 as
teaching data obtained by sampling the running course. The running
course is sampled and stored also when the vehicle is under the
obstacle detouring control by similarly storing the steering angle,
i.e., the running direction .theta., every time the vehicle has
covered the travel distance l.sub.0.
As seen in FIG. 4, the running direction of the vehicle body which
repeats a travel reciprocatingly reverses from travel to travel. In
the subsequent travel, therefore, the running course information
obtained by the teaching of the preceding travel is read out in an
order reverse to the storing order. Thus the data is retrieved from
the memory 25 in response to the signals from the distance sensor
by reversely referring to the address concerned i.e. decrementing
the address.
Further upon lapse of a predetermined period of time after at least
one of the follower sensors 5a, 5B has ceased to detect any unmowed
area during the running course teaching, reference is made to the
running course information l, .theta. obtained by the teaching of
the preceding travel, and the vehicle body 1 is advanced as
forcibly steered toward a direction reversed through 180.degree.
from the running direction .theta. at the corresponding point at a
total travel distance l from the turning area 12D, whereby the
vehicle body is made to automatically run in the desired direction.
This mode of playback control is illustrated in FIG. 7 (C). Under
the playback control, the vehicle body can be so steered that it
will not greatly deviate from the running course even if the course
has an intermediate portion where the follower sensors 5a, 5B are
unable to discriminate between the boundary of running area and the
turning area due to the absence of grass.
Further when the vehicle body is subjected to obstacle detouring
control during running, the running course after detouring the
obstacle 12E is corrected with reference to the running course
information l, .theta. given by the teaching of the preceding
travel. Thus the vehicle body is steered to automatically return to
the specified running course.
When the vehicle body changes its direction at the turning area
12D, the running course information l, .theta. newly taught in the
present travel is block-transferred to the memory area storing the
information of the preceding travel. The vehicle therefore runs
along the boundary of running area under follower control with the
contents of its memory renewed from travel to travel.
In this way, the vehicle is automatically taught the running course
information as to one travel only, so that a memory of greatly
reduced capacity is usable for storing the running course
information l, .theta., while there is no need for the operator to
teach the running course.
FIGS. 7 (A) to (D) are a flow chart showing the operation of the
control unit 13 described above.
* * * * *